Conventionally, tools used in oil and gas drilling, particularly jarring devices (“jars” see e.g. U.S. Pat. Nos. 9,038,744; 8,151,910, respectively entitled: “Jet Hammer” and “Drilling Jar,” both incorporated by reference) were part of the bottomhole assembly (BHA). The BHA is at the lower-end of a drill-string (which is generically referred to as a work string, including both coil tubing and pipe strings; or, generically referred to as a “string” herein). The BHA consists of (from the bottom up in a vertical well) the drill bit, the drill bit sub, optionally, a mud motor (used for driving of the bit hydraulically without rotating the work string), as well as stabilizers, which keep the assembly centered in the hole, a drill collar (heavy, thick-walled tubes used to apply weight to the drill bit) and preferably jars and, as needed, crossovers (adaptors) for fitting together different threadforms on the various components.
Directional drilling is now commonplace, and allows turning a vertical drill string and boring horizontally, or at any angle between horizontal and vertical. Some wells now extend over 10 km from the surface start location, but at a true vertical depth of only 1,600-2,600 m. With directional drilling, and with very deep wells, it's often preferable to place jars at intervals along the string, as well as at the BHA. During drilling of such wells, the drill-string often sticks, and needs to be jarred loose. Other tools may also be preferably placed along the drill string, e.g., shock absorbing tools to aid in stabilizing the bits during drilling; especially useful for rotary drilling (see e.g., U.S. Pat. No. 4,776,410 “Stabilizing tool for well drilling” incorporated by reference). Well bore cleaning tools may also be desired for placement along the string (e.g., U.S. Pat. No. 2,771,141 “Jet Wall Cleaner,”) as well as logging tools (e.g., U.S. Pat. No. 3,638,484), fluid bypass tools (e.g., U.S. Pat. No. 3,845,815) and extended reach tools (e.g U.S. Pat. No. 6,467,557) (all patents incorporated by reference).
During drilling loss of well control is commonplace: due, most frequently, to breaches in the drill string, including “twist-offs”—damage from torsion during drilling. The common means for providing the string a section-by-section system of well control is to use plugs, which are pumped down from the surface and arrested and set by the first nipple profile they encounter in the string. See e.g., U.S. Pat. No. 4,942,925, incorporated by reference. An impediment to placement of tools along the string is that tools generally have a smaller inner diameter than the drill pipe or the outer diameter of a plug. Plugs cannot be pumped past a tool. Therefore, tools are preferably used only at or near the BHA, and not along the string—though they may be needed upstream as well.
Conventionally, where tools are deployed along a string (and because plugs cannot pass them to profile nipples) in order to remedy a loss of well control, repair a damaged or non-functioning tool, or maintain the tool or the string, a wire line is run down from the surface to set a plug in a profile nipple near the BHA. From there, the entire string must be “tripped”—the drill string is pulled up in relatively short sections, each of which are disconnected in sequence, and then stacked, preferably vertically in a rack. After the repair or maintenance, the stacked string sections must be “tripped in.” The tripping of lengthy strings is itself a time-consuming and expensive process, and the process also requires a wire line specialist, and a difficult connection of the wire line with a potentially very distant profile nipple (at the BHA).
Accordingly, there is a need for a simple, cost-effective method of regaining well control, or repairing, replacing or maintaining the string or any tools which are deployed along the string, which can avoid tripping and/or running down a wire-line in the event of problems upstream of the BHA.